Clutch device



Dec. 20, 1949 J. H. PRATT ET AL CLUTCH DEVICE Filed May 20, 1948 2 Sheets-Sheet 1 FIG I.

72 \Si 7 72V O i Inna. VIS 66 2 a 083 92 \0I \2 \3 J. H. PRATT ETAL 2,4913% CLUTCH DEVICE Filed May 20, 1948 2 Sheets-Sheet 2 Patented Dec. 20, 1949 UlTED STATES PATENT OFFICE CLUTCH DEVICE James Henry Pratt, Wythall, and Gilbert Edgar Manley, Norton Curlieu, England Application May 20, 1948, Serial No. 28,126 In Great Britain June 4, 1947 Claims.

This invention has reference to improvements relating to clutch devices and is concerned particularly with clutch devices of the kind comprising a projecting member usually in the form of a rod which is associated with an eye or slot provided in a complementary member in such a manner that the projecting member can slide relatively to the eye or slot when the projecting member is in axial alignment with the axis of the eye or slot and such that movement between the projecting member and the eye or slot is prevented, when canting occurs, due to binding pressure between the Wall of the eye or slot and the projecting member.

In clutch devices of the aforesaid kind the projecting member and eye are usually of a cylindrical formation with the consequence that when binding occurs the binding force is exerted substantially at a point with the result that slip, and undue wear of the co-acting members due to digging in, may obtain and the present invention has for its object to minimise slip and wear in clutch devices of the kind aforesaid.

According to the invention an improved clutch device of the kind hereinbefore referred to is characterised in that the projecting member is made with flattened bearing surfaces and in that the eye or slot is provided with oppositely disposed self-alignable members having flattened bearing surfaces adapted to engage in surface contact with the complementary bearing surfaces of the projecting member when canting obtains for producing the requisite locking of the projecting member and of the complementary member associated with the eye or slot.

An embodiment of the invention will now be described with particular reference to the accompanying drawings which illustrate the invention as applied to a means for preventing the development of lost motion between the brake shoes and the expander mechanism in a two shoe internal expanding brake mechanism for vehicles utilising a Girling expander in which a feeler device is provided for automatically maintaining a substantially constant predetermined running clearance between the said shoes and the brake drum as is described in the specification of our pending United States patent application Serial Number 758,574 filed July 2, 1947.

In the drawings:

Figure 1 is a front view partly in elevation and partly in section of a brake as aforesaid equipped with a clutch device in accordance with the invention the brake being shown somewhat diarammatically.

Figure 2 is a fragmentary view partly in section illustrating the method of connecting to the relevant brake shoe the feeler device employed in Figure 1 for ensuring automatically the maintenance of a predetermined running clearance between the brake shoes and the brake drum, the section being taken on the plane indicated by the line 2-2 in Figure 1.

Figure 3 is a fragmentary view partly in section and on an enlarged scale of the clutch device employed in the construction illustrated in Figure 1.

Figure 4 is a plan of Figure 3 partly broken away and sectioned for the sake of clearness and Figure 5 is a sectional view taken on the plane indicated by the line 5-5 in Figure 3.

Like numerals of reference indicate similar parts in the several views.

,Acoordingto the said illustrated embodiment of the invention the'leading brake shoe 5 has riveted thereto at a position adjacent to the expander mechanism denoted generally by the reference numeral 1 a bracket 8 provided with a short length of inwardly projecting rod Bl of a cylindrical shape-in cross section with the outer portion flattened on the top and bottom as at 82,

see particularly Figures 3 and 5.

Adapted to be passed over this length of rod ll? is the eyed portion 52 formed at the inwardly directed end of an arm 9 the outer end of which is adapted to abut the presented face of the re-- spective plunger H of the expander mechanism 7. The eye 92 is of greater depth than the eye in the case of the construction described in our prior application Serial Number 758,574 as aforesaid and turnably mounted within bearings in the arm adjacent to the eye 92 are the cylindrical ends l l]! of two oppositely disposed pins Ill which are arranged in staggered relationship, see especially Figure 3. Each pin It is provided with a slotted portion I02 having a flat bearing surface ififi and these flat bearing surfaces I03 are presented inwardly and are spaced apart at a distance slightly greater than the depth of the length of rod 8! so that the rod 8! can slide between the flat surfaces I63 of the pins when therod BI is in axial alignment with the eye 92 and so that the pins it can turn to enable the flat surfaces 5 B3 of the pins to align themselves automatically with and to exert surface pressure on the complementary flat surfaces 82, 83 of the rod 8| when the arm 9 is canted.

The arm 9 is engaged pivotally by the inwardly turned ends III of a bent wire hook H to which is anchored one endof a coil spring [2 the opposite end of which is anchored to a pin [3 securedto the back plate I4. The inwardly turned ends I I I of the hook I I are engaged in holes 93 located substantially midway in the sides of the eyed portion of the arm 9 so that the said spring I2 exerts a pull on the arm 9 along a line which is substantially co-axial with the axis of the rod 8| and so as to tend to bring the axis of the eye 92 into coincidence with the axis of the rod 8I so that relative movement between these two parts is possible during the return movement of said parts.

The expander mechanism I which, as has been stated, is of the well known Girling type, incorporates a pair of plungers 'II the inner ends of which are provided with wedge faces I2 between which and the complementary faces of a frustoconical expander I5 are interposed freely displaceable rollers I8 and the braking effort is translated to the said expander I5 by a rod I5I which is connected to the brake operating means not shown.

Associated also with the leading brake shoe 6 is a feeler device generally designated by the reference numeral If. This feeler device I? incorporates a plunger If! the outer end I'I2 whereof is of reduced depth and projects through holes formed in the table SI of the brake shoe 8 and in the friction lining 83 fixed to the outer surface of the said table GI whilst the other end I13 of the plunger I'II abuts a stop I8 carried by the back plate I4.

Intermediate its ends the plunger I'II is provided with an axially arranged elongated slot I'M through which is passed the shank I9 of a headed pin which also passes through a hole in the web B -I of the brake shoe 6. i

A coil spring 20 is interposed between a friction washer 2I located on the shank I9 on the opposite side of the web 64 to the head I9I of the said pin and a washer 2II pinned to the said shank I9 adjacent to the outer end thereof. The spring 20 and friction washer 2| in conjunction with the head I 9| serving to clamp the plunger I'II frictionally between the head I9I and the web 64 of the brake shoe 6.

The leading brake shoe 6 and the companion brake shoe 66 are interconnected by a pull off spring 23 and the degree of friction exerted on the web 64 by the spring 20 and friction washer 2I is arranged to be such that the pull normally exerted by the pull off spring 23 is insufficient to occasion displacement between the plunger III and the web 64 so that whenever braking is being performed the plunger I'II moves with the leading brake shoe 6 and returns with the brake shoe when braking pressure is relieved and arrests the return movement of the brake shoe 6 when the inner end of the plunger Ill abuts the stop I8.

The relationship between the plunger Ill and the stop I8 is determined initially to give a de-- sired predetermined running clearance between the friction surface 63 and the brake drum 2 1 when the inner end I13 of the plunger I'II abuts the stop I8.

In the event of wear of the braking surface contact between the outer end I'I2 of the plunger Ill and the brake drum 24 occasions a displacement of the plunger III relatively to the brake shoe 6 against the resistance offered by the spring 29 and friction washer 2| so that compensation is efiected automatically in the event of wear of the friction surfaces 63 in order to ensure that a substantially constant running clearance obtains at all times between the friction lining 63 of the leading brake shoe 6 and the brake drum 24 whenever braking is not being performed.

The operation of the invention is as follows:

The constant running clearance between the friction lining 63 of the leading brake shoe 6 and the brake drum 25 is maintained automatically by the relative displacement which takes place between the feeler device I? and the brake shoe 6 in the manner described hereinbfore.

When the braking effort is applied, the plunger II of the expander mechanism 7 which transmits the braking effort to the leading brake shoe 6, bears on the outermost end of the eyed arm 9 and by virtue of the canting of the said arm 9 which has been occasioned on the return of the eyed arm 9 to the limit of its return movement after the previous braking operation and which canting is maintained during the operative movement of the plunger II, causes the flat surfaces I83 and the pins II] to bind firmly on the flat surfaces 82 and 83 of the rod 8| so that a positive braking effort is applied to the leading brake shoe 6.

When the braking pressure is relieved the pull off" spring 23 returns the leading brake shoe 8 to the position determined by the inner end I73 of the plunger I'II abutting the stop I8.

In the event of compensation for wear of the friction lining 63 by displacement obtaining between the feeler device I? and the leading brake shoe 6 as set forth hereinbefore there would normally be a space between the plunger I I concerned and the adjacent end of the arm 9 but in accordance with this and the parent invention as the brake shoes 8 and 86 are returned to the full limit permitted by the abutment of the inner end I13 of the plunger III with the stop I8 slip takes place between the eyed arm 9 and the rod 8| so that the spring I2 connected to the said eyed arm 9 can draw the arm a inwardly into abutment with the relevant plunger II so that any lost motion which might develop as a consequence of a compensating adjustment as aforesaid is taken up automatically. Consequently on a succeeding braking operation the same degree of travel only is required from the brake actuating means to effect the requisite movement of the brake shoes 6 and 66 into contact with the brake drum 24.

It is found that the mutual self-alignment between the complementary flattened surfaces I83 of the pins I9 and the flattened surfaces 82, 83 of the rod 8| by ensuring that the whole of the fiat bearing surfaces I83 of the pins I9 come into contact with the complementary flat surfaces 82, 83 of the rod when canting of the arm 9 takes place avoids the concentration of the loads at two points of contact only and thus minimises siip and also wear due to digging in.

In a modification not illustrated the eye may be provided with part spherical recesses within which are located part spherical bearing pads having inwardly presented fiat surfaces adapted to co-act with the flattened surfaces 82, 83 of the rod 8I in an analogous manner to the flattened surfaces I83 of the pins I8. In this modification it will be appreciated that the bearing pads are permitted a universal self-aligning movement.

It will be appreciated that the recessed flat surfaces I93 of the pins I 8 in association with the centrally disposed rod 8i prevent endwise displacement of the pins I8 after the assembly of a clutch device.

Further it will be appreciated that the application of the invention to brake mechanism is given only by way of example as the invention may be applied with advantage to clutch devices of the kind concerned which are employed in other connections Where a heavy binding force is required.

We claim;

1. A clutch device incorporating an eyed member adapted to be engaged by a part required to be operativeiy C0i1i1+ ed by the clutch device, a projecting member which is adapted to be engaged with the complementary part which is required to be operative-1y connected by the clutch device and which is adapted to slide within the eye when the axis of the eye is in axial alignment with the axis of the projecting member, means for causing said axial alignment to obtain on the return movement of the part aforesaid and for causing canting to obtain when the said part reaches the limit of its return movement, flattened bearing surfaces on the projecting member recess of an arcuate shape in cross section formed in the walls of the eye and oppositely disposed members of arcuate cross section self-alignably mounted within said recesses and having flattened bearing surfaces adapted to engage in surface contact with the complementary flattened bearing surfaces of the projecting member when canting obtains for producing the requisite locking of the eyed memher and of the projecting member for effecting an operative connection of the parts associated with the said eyed member and projecting member.

2. A clutch device incorporating an eyed member adapted to be engaged by a part required to be operatively connected by the clutch device said part during an operative movement inducing a canting of the eyed member, a projecting member which is adapted to be operatively connected with the complementary part which is required to be operatively connected by the clutch device and Which is adapted to slide within the eye when the axis of the eye is in axial aligmnent with the axis of the projecting member, spring means for causing said axial alignment to obtain on the return movement of the part aforesaid and for causing canting to obtain when the said part has attained the limit of its return movement, recesses of an arcuate shape in cross section formed in the walls of the eye and oppositely disposed members of arcuate cross section self-alignably mounted within said recess and having flattened bearing surfaces adapted to engage in surface contact with the complementary flattened bearing surfaces of the projecting member when canting obtains for producing the requisite locking of the eyed member and of the projecting member for effecting an operative connection of the parts associated with the said eyed member and projecting member.

3. A clutch device incorporating an eyed member adapted to be engaged by a part required to be operatively connected by the clutch device said part during an operative movement maintaining a canting of the eyed member, a projecting member which is adapted to be operatively connected with the complementary part which is required to be operatively connected by the clutch device and which is adapted to slide within the eye when the axis of the eye is in axial alignment with the axis of the projecting member, spring means for causing said axial alignment to obtain on the return movement of the part aforesaid and for causing canting to obtain when the said part has attained the limit of its return movement, recesses of an arcuate shape in cross section formed in the walls of the eye and oppositely disposed members of arcuate cross section self-alignably mounted Within said recesses and having flattened bearing surfaces adapted to engage in self-alignable bearing contact with the complementary flattened bearing surfaces of the projecting member when canting :obtains for producing the requisite locking of the eyed member and of the projecting member for efiecting an operative connection of the parts associated with the said eyed member and projecting member.

4. A clutch device according to claim 1 in which the oppositely disposed self-alignable members are arranged also in a staggered relationship.

5. A clutch device according to claim 3 in which the self-alignable members are provided with cylindrical outer portions which are turnably mounted in bearings formed in the eyed member and in which the central portions of the said members are recessed and provided with flattened surfaces for co-operation with the flattened surfaces of the projecting member.

JAMES HENRY PRATT.

GILBERT EDGAR MANLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 664,083 Harthan Dec. 18, 1900 784,938 Hall Mar. 24. 1905 979,703 Ross Dec. 27, 1910 1,227,941 Sauvage May 29, 1917 

